Abstract: Sepsis is responsible for a large number of hospitalizations and it is often associated with cause of death in hospital environment. It is a disease eventually hard to diagnose, whether clinical or laboratory, due to nonspecific signs and symptoms in patients and the treatment with antibiotics is generally empiric since there are no specific markers for sepsis and may lead to abuse of antibiotics and therefore may increase the risk of developing bacterial resistance. Objective. This study aims to evaluate the ability of procalcitonin (PCT), a calcitonin prohormone to guide antibiotic therapy in patients of the Adult Intensive Care Unit of HC-UFPR, reducing days of antibiotic therapy when compared to empirical therapy in a control group. Procalcitonin (PCT) is a prohormone of calcitonin produced by several cells and organs after pro inflammatory stimulation, especially bacterial. After a unique and acute stimulation PCT presents long half-life in vivo, approximately 20-24h, compared to other parameters; moreover, PCT shows rapid and highly specific increase in response to bacterial systemic infections and sepsis. Method. We evaluated 32 patients randomized into two groups, PCT and control. For the group control the conduct was the same that were used in the ICU, based on clinical and laboratory findings and the PCT group, the protocol suggested in this study proposes to begin the therapy based on PCT levels >0,5ng/mL, and revaluation on fifth day. Patients will be assessed at admission (D0) and followed at D3, D5 and D10. Were also assessed severity scores, PCT values and C-reactive protein for survivors and non-survivors. Results. We observed the same mortality between both groups during follow-up protocol, an overall mortality of 46.8% by the 28th day and there was no statistically significant difference in survival between the two groups. There was no correlation between PCT x PCT and PCR x WBC in any of the evaluated days (D0, D3, D5, D7 and D10). In the ITT analysis, the treatment duration for the control group was 11 days (5-25) and the PCT Group 10 days (4-16), but the difference did not reach statistical significance (p = 0,65). As for the length of stay in the ICU there was no difference between the groups, with a median of 15.5 days (9-30) for the control group and 12.5 days (7-28) for the PCT group, p = 0, 79. When compared survivors and non-survivors, there was a statistically significant difference in PCT D0, D0 SOFA, APACHE II and IV, the Delta SOFA and Highest SOFA. The cost of treatment per patient in the PCT group was R$ 1,074.20 and in the control group of R$ 1,213.20. In the PCT group was observed savings of R$ 139.00 per patient, approximately 11.5% when compared to the control group. Conclusion. There was no significant reduction in days of treatment, but a saving in the PCT treatment group. Patients more critical and who died had higher value of PCT in D0, as well as scores APACHE II and IV, SOFA, Delta SOFA and Highest SOFA. Key-words: sepsis, procalcitonin, antibiotic, ICU